The present invention relates to an engine having a vertically disposed crankshaft, that is used, for example, in lawn mowers and the like.
In a conventional engine having a vertically disposed crankshaft (a vertical crankshaft type engine), which is supported in cantilever fashion, as disclosed in the Japanese Utility Model Laid-Open No. 60-57749, a space between a dust guard cover and a crankcase is used as an intake opening or inlet for a cooling air.
However, in such a conventional vertical crankshaft type engine, since the air intake inlet is formed in a portion of the periphery of the engine, an area of the intake inlet is relatively small, and accordingly, there arises a problem that it is necessary to increase velocity of the cooling air flow in order to obtain a predetermined amount of the cooling air. Further, since the whole air intake inlet of wide cross-sectional area is opened to the atmosphere, there arises another problem that the cut lawn and/or dust are/is introduced into the interior of the engine body through the cooling air intake inlet, whereby the cut lawn and/or dust are/is adhered to fins of cylinders of the engine and are/is burnt thereon, or the cut lawn or the like is jammed in the air passage to worsen cooling ability.